When a load mounted on a vehicle is operated, a command signal is transmitted from a higher-level controller that controls the operation of the load to a lower-level controller that actually operates the load via a network in the vehicle. At this time, when a plurality of loads is operated at different timings, for each load, a command signal corresponding to the operation timing of the load is transmitted from the upper controller to the lower-level controller.
For example, when ten LED devices mounted on a vehicle as lighting devices in the interior of the vehicle are caused to emit light in white at a little intervals, ten kinds of command signals corresponding to light emission patterns of the LED devices are transmitted from the higher-level controller to the lower-level controller that operates each LED device via the network inside the vehicle (see JP 2017-084573 A (patent family: US 2017/0118816 A1)).